Lathes have long been used to turn metal and wooden parts. In a lathe, the lathe spindle retains the workpiece via a workpiece holder mounted thereon. The workpiece holder is cause to rotate, and a cutting tool is brought into contact with the rotating workpiece to cause removal of material from the workpiece. The resulting form is symmetric about its axis of rotation.
In many cases, it is desired to produce forms that are not symmetric about an axis of rotation. For example, automotive pistons typically are designed to have ovoid or elliptical forms. It can be difficult to produce pistons and other parts having an ovoid shape on a lathe, and it can be difficult to produce other complex shapes on a lathe. Conventionally, in many embodiments such forms either may be milled or otherwise machined, or turned on specialized lathes. Various approaches are purportedly described in U.S. Pat. Nos. 5,313,694, 6,202,521 and 6,760,961, and U.S. Patent Publication Serial No. US2003/0209394.